The 7 Percent Solution
The problem was to find the right laws of beta decay. There
appeared to be two particles, which were called a tan and a theta. They seemed to
have almost exactly the same mass, but one disintegrated into two pions, and the other into three pions. Not only did they seem to have the same
mass, but they also had the same lifetime, which is a funny coincidence. So everybody was concerned about this.
At a meeting I went to, it was reported that when these two particles were produced in a cyclotron at different angles and different energies, they
were always produced in the same proportions--so many taus compared to so many thetas.
Now,
one possibility, of course, was that it was the same particle, which sometimes decayed into two pions, and sometimes into three pions. But
nobody would allow that, because there is a law called the parity rule, which is based on the assumption that all the laws of physics are mirror-image
symmetrical, and says that a thing that can go into two pions can't also go into three pions.
At that particular time I was not really quite up to things: I was always a little behind. Everybody seemed to be smart, and I didn't
feel I was
keeping up. Anyway, I was sharing a room with a guy named Martin Block, an experimenter. And one evening he said to me, "Why are you guys so
insistent on this parity rule? Maybe the tau and theta are the same particle. What would be the consequences if the parity rule were wrong?"
I thought a minute and said, "It would mean that nature's laws are different for the right hand and the left hand, that there's a way to define the
right hand by physical phenomena. I don't know that that's so terrible, though there must be
some bad consequences of that, but I don't know. Why
don't you ask the experts tomorrow?" , -
He said, "No, they won't listen to me.
You
ask."
So the next day, at the meeting, when we were discussing the tau-theta puzzle, Oppenheimer said, "We need to hear some new, wilder ideas
about this problem."
So I got up and said, "I'm asking this question for Martin Block: What would be the consequences if the parity rule was wrong?"
Murray Gell-Mann
often teased me about this, saying I didn't have the nerve to ask the question for myself. But that's not the reason. I thought it
might very well be an important idea.
Lee, of Lee and Yang, answered something complicated, and as usual I didn't understand very well. At the end of the meeting, Block asked nie
what he said, and I said I didn't know, but as far as I could tell, it was still open--there was still a possibility. I didn't think it was likely,
but I thought
it was possible.
Norm Ramsey asked me if I thought he should do an experiment looking for parity law violation, and I replied, "The best way to explain it is, I'll
bet you only fifty to one you don't find anything."
He said, "That's good enough for me." But he never did the experiment.
Anyway, the discovery of parity law violation was made, experimentally, by Wu, and this opened up a whole bunch of new possibilities for beta
decay theory, It also unleashed a whole host of experiments immediately after that. Some showed electrons coming out of the nuclei spun to the left,
and some to the right, and there
were all kinds of experiments, all kinds of interesting discoveries about parity. But the data were so confusing that
nobody could put things together.
At one point there was a meeting in Rochester--the yearly Rochester Conference. I was still always behind, and Lee was giving his paper on the
violation of parity. He and Yang had come to the conclusion that parity was violated, and flow he was giving the theory for it.
During the conference I was staying with my sister in Syracuse. I brought the paper home and said to her, "I can't understand these things that
Lee and Yang are saying. It's all so complicated."
"No," she said, "what you mean is
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